The use of security systems for personal computers is generally known in the art. For example, U.S. Pat. No. 4,951,249 discloses a computer security system which protects computer software from unauthorized access by requiring the user to supply a name and a password during the operating system loading procedure ("boot-up") of a personal computer (PC). This is accomplished by the insertion of a special card into an input/output expansion slot of the PC. During operating system loading of the PC, the basic input/output system (BIOS) scans memory addresses of the card for an identification code, which consists of a 55AA hex code. When this hex code is located, the BIOS instructions are vectored to that address and the instructions that follow that address are executed as part of the initialization routines of the system boot-up procedure.
The special card comprises a board with a read only memory (ROM) and an address decoder, and prevents system boot-up via the PC's floppy drive by intercepting the floppy drive interrupt, so that it appears to the processor that the PC does not have a floppy drive. The keyboard is also disabled by capturing the keyboard interrupt. As a result, the PC is forced to boot-up using the software on the card.
The foregoing PC security system, which utilizes a password board, is typical of many of the systems which are currently available. Password boards require a user's name and a password associated with that user's name. Only once a password board detects a valid user's name and password does it allow the PC to complete the boot-up routine. While password boards may be useful under some circumstances, they are inadequate in many respects.
For example, password boards provide security only during initialization of the PC; they provide no security for the system should the operator leave it unattended during the day. In addition, many PCs do not have an open architecture that allows additional circuit cards to be plugged into the system. Furthermore, as personal computers get smaller there are fewer slots available for upgrading the system with graphic, memory, and coprocessor boards.
Also, password board security systems are placed between the operating system and any application that the user may run. While this method is compatible with MS-DOS and PC-DOS, it is not always compatible with Windows or other higher level operating systems. As usage of these other operating systems becomes more widespread, the password board security systems are of increasingly limited utility.
An additional limitation of password board security systems is that such systems do not enable monitoring of access and usage of the PC. Such systems do not create a record of both authorized and unauthorized attempts to access the PC which can later be retrieved by the PC owner or administrator.